As a general proposition it may be fairly stated that over the years the field of electronic components has experienced a continuous reduction in component size while simultaneously calling upon these components to handle increasingly greater levels of power. An over-simplification would be to say that smaller size and increased power levels result in higher operating temperatures for the electronic components. The presence of elevated temperatures of the electronic component is attended by a variety of operational difficulties and malfunctions, all of which are temperature related.
In the use of a solid state component or device, the presence of high power levels results in high temperature operation which causes distortions in the operating characteristics of the device. In the worst case situation, absent the removal of the heat liberated during such operation, a complete failure of the component or device will occur.
Distortions or deformations in physical parameters of such devices as laser mirrors used in conjunction with high energy laser beams is yet another technical area where there is an uncommonly high level of energy in a small area that must be removed, least unwanted deformations in the mirror occur due to heat liberated by the laser beams cooperation with the reflective surface of the mirror.
When the device to be cooled is in the form of a mirror there are technical considerations in respect of the total physical nature of the mirror that must be taken into account. These considerations are such as, but not limited to the desirability of (1) the mirror being capable of handling increased laser power, (2) a reduced level of vibration to the mirror surface induced by whatever means are used to cool the mirror, and (3) mirror face plate temperature uniformity.
Also to be considered in a mirror environment are such additional considerations as mirror wedging, a phenomena induced by the presence of a temperature gradient along the face of mirror face plate, as well as a deformation termed inter-actuator bowing which is purportedly due to a face plate temperature rise over a substrate upon which the mirror is positioned.
The invention to be described more fully hereinafter is especially useful as a means for providing cooling for a heat liberating device such as a high power laser mirror. The problem of removing large quantities of heat from a small area is also encountered in the prior art systems for cooling electronic circuits. A review of the prior art has uncovered a number of cooling systems and cooling apparatus, that taken collectively, establish a background against which the invention to be described, advantageously departs from and will be defined over. In view of the fact that the invention to be described in this specification deals with impingement cooling, the prior art set forth next and then distinguished over, will all be of the type where at least some facet of the cooling apparatus utilizes impingement cooling of a heat liberating device.
The patent to P. G. Ross, U.S. Pat. No. 3,400,543 is directed to a semi-conductor cooling means which utilizes a fluid injection system to cool the base member of a transistor. Ross employes, as seen in FIG. 2, a single jet of coolant delivered through an injection tube 44 to the base of a semi-conductor 10. Ross has a fluid return means 54 (FIG. 1) which receives coolant after impingement. Ross does not provide, as does the invention of this specification, for arrays of submerged fluid jets, nor an arrangement of stacked heat conducting plates designed to provide an array of submerged jets and coolant delivery and drainage means integrally formed by the plates in combination with a housing upon which the device to be cooled is mounted.
The next three patents to R. M. Hruda, U.S. Pat. No. 3,414,753, H. Kawamoto, U.S. Pat. No. 3,908,188 and S. W. Kessler, U.S. Pat. No. 4,258,383 to be reviewed, suffer from the same deficiencies noted in respect of Ross above.
Accordingly, we see in R. M. Hruda, the removal of vaporized cooling liquid from heat exchange elements by power jets. Hruda provides a plurality of vertically disposed pipes 28 having openings 49 through which coolant is directed towards an anode or target element 16 submerged in the coolant. The impingement jets from openings 40 break up a vapor layer on element 16 formed in boiling heat transfer.
The patent to Kawamoto is directed to an individual heat sink for a solid state element and employs a single impingement jet 8 directed at the base of the solid state element.
The patent to S. W. Kessler is directed to a minimum pressure drop liquid cooled structure for a semiconductor device. Kessler teaches a technique to optimize heat transfer to effect cooling and pressure drop for radial flow across a flat surface. A conduit 36 delivers coolant in a direction normal to the surface from which heat is to be removed. At the end of conduit 36 there is provided a flange 42 that has a frustoconical face 50 formed thereon to thereby allow coolant to be directed towards the surface to be cooled while optimizing pressure drop for the radial flow across the surface to be cooled.
The patent to E. C. Leaycraft, U.S. Pat. No. 4,296,455 is directed to slotted heat sinks for high powered air cooled modules. Leaycraft provides for a parallel air flow of large volume to be directed through openings 18 in a plate 17 to impinge directly onto an integrated circuit module 10. Although Leaycraft characterizes the flow as impinging, the size of the openings 18 which are nearly the same size as the component to be cooled would more aptly be considered area cooling rather than impingement cooling of the jet type described in the patents reviewed hereinbefore.
Leaycraft does not suggest as does the invention to be described, the provision of submerged fluid jets arranged in an array that envolves a heat conducting fin like structure coupled to the device to be cooled, the fins having orifices therein positioned such that coolant delivered to and through the fin orifices creates the submerged array of jets that allow the removal of heat from the fins which in turn provide for cooling of the device.